Evidence review: Open Peptide Project (verified against primary PubMed, ClinicalTrials.gov & FDA records) · Last checked 2026-10-26. ← Back to Evidence Library

IGF-1 (mecasermin): what the evidence says

Name: IGF-1 (mecasermin)
Published: 2026-10-26

At a glance

What it is: lab-made human insulin-like growth factor-1, the 70-amino-acid hormone that carries most of growth hormone's growth effects. Sold as Increlex (mecasermin). Gray-market "IGF-1" vials usually mean this or the modified forms on separate pages (IGF-1 LR3, IGF-1 DES). ^{R1, R2}

What the evidence says: FDA-approved only for growth failure in children 2 years and older with severe primary IGF-1 deficiency (for example Laron syndrome) or GH gene deletion with GH antibodies. In a 76-child open trial, growth speed rose from 2.8 to 8.0 cm/year in year 1. ^{R1, R2} No controlled trial supports muscle, fat-loss or anti-aging use.

Biggest risks: low blood sugar (including seizures), allergic reactions and anaphylaxis, raised skull pressure, tonsil and adenoid overgrowth, and cases of malignant tumors in treated children. ^{R1, R3}

Rating


Human Human evidence	Moderate for the approved pediatric use (open-label trials and a 306-patient registry) ^{R2, R4, R3} · Very limited for other conditions (e.g., a 12-girl Rett syndrome phase 1) ^R5 · No controlled data for muscle, fat loss, anti-aging
Animal Animal / lab evidence	Not reviewed for this page
Regulatory	FDA-approved (Increlex, BLA 021839) for one rare pediatric use · not on the 503A/503B lists · WADA 2026: prohibited at all times (S2.3) ^{R6, R7, R8, R9}
Established human dose	Only for the approved pediatric use, per the label. Study details lists what studies used

Evidence verdict: Growth failure in children with severe primary IGF-1 deficiency (approved use): Moderate · Muscle, fat loss, anti-aging in healthy adults: No controlled human data

This page reports what studies used. It is not dosing advice.

Legend: HUMAN data · ANIMAL / LAB data · UNKNOWN · UNVERIFIED: not yet confirmed against a primary source

About the evidence: the approval rests on small, uncontrolled trials in a very rare condition; a randomized placebo trial would be unethical in these children. The registry is run with the maker (Ipsen, later Esteve). ^{R2, R4}

What is it?

IGF-1 is made mainly in the liver in response to growth hormone and acts much like insulin on blood sugar. Mecasermin replaces it when the body cannot respond to GH. ^R2 Related pages: Human growth hormone, IGF-1 LR3, IGF-1 DES, MGF.

Does it work?

Human Severe primary IGF-1 deficiency: growth speed 2.8 → 8.0 cm/year in year 1, staying above baseline up to 8 years (n = 76, open label). ^R2 In a European registry, 56% of children without Laron syndrome responded well; younger age predicted better growth. ^R4
Human Rett syndrome: phase 1 in 12 girls showed it reached the brain and was tolerated; efficacy was only preliminary. ^R5
Unknown No trial in healthy adults for muscle, fat loss, recovery or anti-aging.

Is it safe?

Human Low blood sugar: the most common adverse event; 80 of 304 registry children had at least one episode, more often with Laron syndrome or a prior history. ^{R3, R4} The label warns of hypoglycemic seizures and says to take it with a meal or snack. ^R1
Human Other label warnings: allergic reactions including anaphylaxis, intracranial hypertension, tonsil/adenoid overgrowth, slipped hip growth plate, worsening scoliosis, and several cases of malignant neoplasia in treated children. ^R1 A case report describes an allergic reaction. ^R10
Unknown No safety data for healthy adults.

Gray-market "research use only" IGF-1: extra risks

A gray-market vial has no quality control and no guarantee of identity, strength or sterility. We test retail vials blind under the Open Peptide Standard; see /tests/. A passing test covers one batch on one date and does not mean the compound is safe. Because IGF-1 lowers blood sugar like insulin, an over-strong or mislabeled vial can cause dangerous hypoglycemia. ^R1

What we don't know

Unknown Any benefit in healthy adults
Unknown Long-term cancer risk with non-medical use

Is it legal?

US (FDA): prescription only, approved for one rare pediatric use; the label says it is "not a substitute to GH." ^{R1, R6} Not on the 503A or 503B bulk-substance lists or FDA's safety-risk page. ^{R7, R8, R11}
Athletes: WADA 2026 S2.3 names IGF-1 (mecasermin) and its analogues; prohibited at all times. ^R9

Study details

These are amounts researchers used, not recommendations.

Study	People / model	Route	Amount used	Follow-up	Reported	Citation
Mecasermin pivotal trial	76 children with severe IGF-1 deficiency	Subcutaneous	0.12 mg/kg twice daily	Mean 4.4 years	Growth 2.8 → 8.0 cm/year in year 1	PMID 18481900
Rett phase 1 (Khwaja 2014)	12 girls with MECP2 mutations	Subcutaneous	40–120 µg/kg twice daily	4 weeks + 20-week extension	No hypoglycemia or serious adverse events	PMID 24623853

Full reference list (PubMed, CT.gov, FDA and WADA checked Oct 26, 2026)

^R1 Increlex (mecasermin) prescribing information, BLA 021839, label effective Aug 5, 2025 (DailyMed). https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a8b27a1b-a611-4f91-ad22-76d4b390c3ae
^R2 Keating GM. BioDrugs. 2008. PMID 18481900
^R3 Bang P, et al. J Clin Endocrinol Metab. 2023. PMID 37579214
^R4 Bang P, et al. Eur J Endocrinol. 2021. PMID 33434161
^R5 Khwaja OS, et al. Proc Natl Acad Sci U S A. 2014. PMID 24623853
^R6 Drugs@FDA, Increlex (mecasermin), application 021839 (checked Oct 26, 2026). https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=021839
^R7 FDA, 503A bulk drug substances categories list (updated May 14, 2026). https://www.fda.gov/media/94155/download
^R8 FDA, 503B bulk drug substances categories list (updated Mar 21, 2025). https://www.fda.gov/media/94164/download
^R9 WADA. The 2026 Prohibited List, S2.3. https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf
^R10 Metz KA, et al. Ann Allergy Asthma Immunol. 2009. PMID 19663134
^R11 FDA, Certain bulk drug substances for use in compounding that may present significant safety risks (content current Apr 22, 2026). https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks

Disclaimer

This page is for education and harm reduction, not medical advice or a recommendation to use IGF-1 (mecasermin). Talk to a clinician you trust, especially if you have diabetes or low blood sugar episodes, a current or past cancer, are pregnant, or are a tested athlete. Report problems to FDA MedWatch (https://www.fda.gov/safety/medwatch).